RSS, ATOM, and Related Technologies Forum

Assume I want to create a master event calendar, showing all the events of a dozen sub-chapters of a club. Let's say it's an outdoor club with a hiking, biking, canoeing subchapters and I also want to publish a single all-inclusive list.

Is there an XML schema available, similar perhaps to RSS, which I could use? How can multiple independent organizations share or aggregate calendar data?